In general, the construction machine such as a hydraulic excavator, a hydraulic crane and the like starts/stops an engine on the basis of an operation of a key switch by an operator. More specifically, the operator of the construction machine inserts a plate-shaped or rod-shaped key into a key cylinder of a key switch when the engine is to be started and rotates this key. In this case, when a key groove of the key and a key cylinder groove match each other, the key becomes rotatable.
By the operator, the key is rotated to any one of an “OFF” position where electric equipment of the construction machine is not conducted and the engine is stopped, an “ON” position where the electric equipment is conducted, and a “START” position where the engine is started (a starter motor of the engine is rotated) (Patent Document 1), for example.
Here, engine start of the construction machine is performed in a state where a position of a gate lock lever provided in the vicinity of an operator's seat is set to a lock position (prohibition position) where driving of a hydraulic actuator is prohibited. When the key is rotated from the position of “OFF” to the position of “START” over the position of “ON” in this state, the starter motor of the engine is rotated, and the engine is started. At this time, in the case where an operation of the key is stopped, and the key is brought into a free state, the key returns from the position of “START” to the position of “ON”, and an “engine driven/conduction ON” state is brought about where the electric equipment is conducted in a state where the engine is driven.
On the other hand, in the case where the key is rotated from the position of “OFF” to the position of “ON”, an “engine stopped/conduction ON” state is brought about where the electric equipment is conducted or connected while the engine is stopped. In the case where the key is further rotated from the position of “ON” to the position of “OFF”, the electric equipment is brought into a non-conducted or shut-down state, and in the case where the engine is driven at this time, the engine is stopped.